I was only sort of kidding with the imaginary Wambayama RC,
If we aren't limiting to vintage (whatever that means right now) I do think its a 1/1 card with all of the bells and whistles and autographed by at least one person... Probably its a card from a sport that has international appeal -- soccer (futbol) or maybe basketball. It's got to be a card of someone with boundless potential. Maybe a card that includes autos from someone like Wambayama with those of Jordan and Lebron. Or maybe Sabrina Ionescu who I think is the future of Women's hoops with a Kobe Bryant auto on it? Kobe was a big fan of hers and she spoke at his memorial.
https://www.youtube.com/watch?v=1-z5lkrVL9Q
Its also possible that the name and likeness rules for NCAA athletes will generate some Rookie (or pre-Rookie) cards that will entice speculators and bring college sports fans into the game too? How about some 1/1 father and sons autographed cards with Lebron James and his sons ?
If we are really talking about vintage (aren't we supposed to be talking vintage?) I'm thinking a high grade (9 or 10) of a marquee card of an all-time great. Maybe one of the 3 extant PSA 8 T205 Cobbs (none higher) or the 1/1 PSA 10 Goudey Baba Ruth #181. For the 50's I'll go with the 1/1 PSA 10 1952 Willie Mays.
More recently I'll take whatever Star Co. RC card of Michael Jordan gets the highest grade.
I'm not necessarily agreeing that these cards are the best just the one's I think will go through the roof if/when they come to auction.
Personally I'm not that into grading premiums but really rich people like to own the best specimens.